The present disclosure relates to image forming apparatuses exploiting electrophotography, such as copiers, printers, facsimile machines, and multifunction peripherals having the functions of those. More particularly, the present disclosure relates to charging devices provided with a charging member for electrostatically charging an image carrying member, image carrying member units having an image carrying member and a charging device integrated into a unit, and image forming apparatuses provided with them.
Conventionally, in an image forming apparatus, a charging device is used to electrostatically charge the surface of a photosensitive drum as an image carrying member. A charging device can be one adopting a corona charging method, according to which a photosensitive drum and a corona wire are arranged with no contact with each other and the surface of the photosensitive drum is electrostatically charged by corona discharge, or one adopting a contact charging method, according to which a charging member such as a charging roller is brought into contact with the surface of a photosensitive drum to electrostatically charge it. In recent years, however, with a view to reducing the emission of ozone, which is hazardous to the human body, the contact charging method, which emits less ozone, is increasingly preferred to be adopted.
Such a charging device is often integrated, along with a photosensitive drum, into a unit called an image carrying member unit, and to allow maintenance, replacement, and the like of the charging device, the charging device is removably attached to the unit main body.
On the other hand, in recent years, such structures have been proposed as permit a photosensitive drum and a charging roller to be taken apart from each other; for example, an electrophotography process unit is known that is provided with retracting operation means whereby, when a charging unit is taken out of the electrophotography process unit, a charging roller is taken apart from a photosensitive member to be retracted by being moved in the axial direction of the charging roller from the position for charging the photosensitive member unit and a rotating mechanism for rotating about the axis of the charging roller in the process of retraction operation by the retraction operation means.